Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$86.30	13.487%	$97.9393	$97.94	$97.95	$97.90
Purchase #2	$67.85	4.317%	$70.7791	$70.78	$70.80	$70.80
Purchase #3	$231.72	12.299%	$260.2192	$260.22	$260.20	$260.20
Purchase #4	$227.93	8.648%	$247.6414	$247.64	$247.65	$247.60
Purchase #5	$184.55	6.544%	$196.627	$196.63	$196.65	$196.60
Purchase #6	$172.95	3.712%	$179.3699	$179.37	$179.35	$179.40
Purchase #7	$25.53	12.448%	$28.708	$28.71	$28.70	$28.70
7 purchase totals =	$996.83		$1,081.2839	$1,081.29	$1,081.30	$1,081.20